Oxidised cellulose and its derivatives have been widely used in medicine and pharmacy since the first preparation by Chait and Kenyon [Shorygin P P., Chait E. V.: Zh. obshch. chim. 7, 188 (1937); Yackel E. C., Kenyon W. O.: J Am. Chem. Soc. 64, 121 (1942)].
Other types of haemostatics and antifibrinolytics have been introduced, however, oxidised cellulose especially in the highly pure form of a polyanhydroglucuronic acid and their copolymers (PAGA), and notably salts thereof, is used in various medicinal applications as a completely resorbable semi-synthetic polymer with minimum adverse effects in the organism. This is true for both the basic substance prepared according to GB 709684; U.S. Pat. No. 4,100,341, or salts thereof prepared according to more recent patents, such as.: CS AO 242920; EP 0659440A1 and PCT IE 98/00004.
It is known that after application of oxidised cellulose to stop surface bleeding a rigid scab is formed, especially on movable parts of the body, such as knees, fingers or ankles. This may be a disadvantage because it can crack and lead to renewed bleeding. Using a haemostat according to PCT IE 98/00004 this disadvantage can be partially overcome by altering the technological conditions of the manufacture (such as increasing the amount of crosslinks) which brings about increased accumulation of the body fluids in the substance and thereby the flexibility of the wound cover is optimised.
Within the last two decades, during investigations of various types of polysaccharides, it was established that during their biodegradation in the living organism certain functions of various types of cells are influenced. [Berger J., Nemec J., Sedlmayer P., Vortel V.: Report on Toxicological Investigation of a New Drug Preparation xe2x80x9cMikrocelxe2x80x9d, Internal report, Research Institute for Pharmacy and Biochemistry, Praha, branch Pardubice-Rosice and Labem, 1984; Burchard W.: Polysacharide, Eigenschaften und Nutzung, Springer-Verlag, Berlin, Heidelberg, New York, Tokyo, p. 144 (1985); U.S. Pat. No. 5,166,137]. Depending on the type of bond in the main glycosydic chain, on the value of the degree of polymerisation, on the presence of various functional groups, and the degree of ionisation thereof, on the type of structural units, and the type of salt or a complex salt thereof, these polysaccharides affect the immune system of the organism. It seems for instance that glucanes bonded by an 1,3 xcex2 bond have immunomodulative properties while 1,4 xcex2 bonded glucanes suppress tumorous growth. There are however exceptions to these rules. An important factor underlying these properties is the presence of the glucuronic acid in the chain.
It is known that a large proportion of bonds between individual substances occurring in living organisms is of a non-covalent nature, such as hydrogen bonds, van der Waals forces, or bonds of an ionic character especially with biopolymers. These bonds create so-called intermolecular polymeric complexes (IMC) such as for example, heparin-peptides. In general these complexes represent a new class of macromolecular substances formed by association of individual polymer chains into macromolecules through secondary bonding interactions. According to the nature of the interactions these complexes can be subdivided into polyelectrolyte complexes, hydrogen bonded complexes, stereo complexes and charge transfer complexes. These types of complexes have a number of common properties, notably an organised supermolecular structure and the ability to create other higher supermolecular entities. The characteristic feature is their ability to undergo restructuring depending on the conditions prevailing in their environment. Further they are capable of undergoing interpolymer substitution reactions and it is especially due to this latter ability that the IMCs in their behaviour come close to imitating biochemical processes occurring in living organisms.
The invention in particular involves the use of polyanhydroglucuronic acids and salts thereof. The term polyanhydroglucuronic acid and salts there of as used herein also includes copolymers thereof, especially with anhydroglucose. This is hereinafter referred to as PAGA.
Co-pending patent application PCT IE98/00004 describes particular polyanhydroglucuronic acids and salts thereof and a method of preparing such compounds. In particular therefore, the term polyanhydroglucuronic acids and salts thereof includes the acids and salts referred to in this co-pending application.
According to the invention there is provided a biocompatible intermolecular polymer complex of:
an anionic component comprising a linear or branched polysaccharide chain wherein at least 5% of the basic structural units are glucuronic acid; and
a non protein cationic component comprising a linear or branched natural, semi-synthetic or synthetic oligomer or polymer.
In a preferred embodiment of the invention the cationic component contains nitrogen that either carries a positive charge or wherein the positive charge is induced by contact with the polysaccharidic anionic component.
In one case the cationic component is selected from derivatives of acrylamide, methacrylamide and copolymers thereof. Preferably the cationic component is selected from polyacrylamide, copolymer of hydroxyethylmethacrylate and hydroxypropylmetacrylamide, copolymers of acrylamide, butylacrylate, maleinanhydride and/or methylmetacrylate.
In another case the cationic component is a cationised natural polysaccharide. Preferably the polysaccharide is a starch, cellulose or gum. The gum may be guargumhydroxypropyltriammonium chloride.
In another case the cationic component is a synthetic or semi-synthetic polyamino acid. Preferably the cationic component is polylysin, polyarginin, or xcex1,xcex2-poly-[N-(2-hydroxyethyl)-DL-aspartamide].
In a further embodiment the cationic component is a synthetic anti-fibrinolytic. The anti-fibrinolytic may be a hexadimethrindibromide (polybren).
In a still further embodiment the cationic component is a natural or semi-synthetic peptide. Preferably the peptide is a protamine, gelatine, fibrinopeptide, or derivatives thereof.
In a further case the cationic component is an aminoglucane or derivatives thereof. Preferably the aminoglucane is fractionated chitin or its de-acetylated derivative chitosan. The aminoglucane may be of microbial origin or is isolated from the shells of arthropods such as crabs.
In a preferred embodiment of the invention the anionic component is polyanhydroglucuronic acid and/or biocompatible salts thereof.
In this case preferably the polyanhydroglucuronic acid and salts thereof contain in their polymeric chain from 8 to 30 percent by weight of carboxyl groups, at least 80 percent by weight of these groups being of the uronic type, at most 5 percent by weight of carbonyl groups, and at most 0.5 percent by weight of bound nitrogen. Preferably the polyanhydroglucuronic acid and salts thereof contain in their polymeric chain at most 0.2 percent by weight of bound nitrogen.
In a preferred embodiment the molecular mass of the polymeric chain of the anionic component is from 1xc3x97103 to 3xc3x97105 Daltons, ideally, the molecular mass of the polymeric chain of the anionic component ranges from 5xc3x97103 to 1.5xc3x97105 Daltons.
Most preferably the content of carboxyl groups is in the range of from 12 to 26 percent by weight, at least 95 percent of these groups being of the uronic type.
In a preferred embodiment of the invention the anionic component contains at most 1 percent by weight of carbonyl groups.
The carbonyl groups are preferably intra- and intermolecular 2,6 and 3,6 hemiacetals, 2,4-hemialdals and C2-C3 aldehydes.
The cationic component may be gelatine.
Alternatively the cationic component is chitosan.
The invention also provides a pharmaceutical or cosmetic composition including at least one biocompatible complex of the invention.
Preferably the composition includes at least one biocompatible biologically active substance.
The composition may alternatively or additionally include at least one biologically acceptable adjuvant.
We have now found that by preparing polymeric intermolecular complexes (IMC) of glucoronoglucanes, notably microdispersed PAGA, prepared especially, according to PCT IE 98/00004 it is possible to enhance the haemostatic effect of the final products on this basis and the properties of the temporary wound cover formed after the haemostasis is achieved such as its flexibility and resistance to cracking on movable parts of the body.
It is also possible to upgrade physicomechanical properties of the final products on this basis. Such IMCs make it possible to prepare application forms whose manufacture from a pure PAGA or their simple salts is extremely difficult. Such application forms includes non-woven textile-like structures or polymeric films. To modify or upgrade the physical mechanical properties it is sufficient to use even a relatively small amount of polymeric counterion while it is possible to obtain suitable application properties within a broad concentration range of the components. The ratio of the glucuronoglucane to polymeric counterion can be 0.99:0.01 to 0.01:0.99.
Another advantage of glucuronoglucane based IMCs is the possibility to control their biological properties such as varying the degree of haemostatis, resorption time, or immunomodulative properties, and the like.
Polymeric cations suitable to form IMCs with glucuronoglucanes prepared for example according to PCT IE 98/00004 may roughly be subdivided into the following groups:
1. Synthetic biocompatible nitrogen-containing oligomers and polymers.
a) Derivatives of acrylamide and methacrylamide and their copolymers [such as polyacrylamide, copolymer of hydroxyethylmetacrylate and hydroxypropylmetacrylamide, copolymer of acrylamide, butylacrylate, maleinanhydride, and methylmetacrylate, and the like], or else cationised natural polysaccharides such as starches, celluloses, or gums such as guargumhydroxypropyltriammonium chloride.
b) Synthetic or semi-synthetic polyaminoacids such as polylysin, polyarginin, xcex1,xcex2-poly-[N-(2-hydroxyethyl)-DL-asparamide. Synthetic antifibrinolytics hexadimethrindibromide (polybren) can also be included in this group.
2. Natural or semi-synthetic peptides such as gelatine, protamines, or fibrinopeptides, and their derivatives.
3. Natural aminoglucanes such as fractionated chitin and its de-acetylated derivative chitosan, of microbial origin or isolated from the shells of arthropods such as crabs.
In preparing IMCs on the basis of PAGA according to the invention these three groups of substances can be combined to obtain required properties of the final product.
In general it can be said that IMCs using substances from 1a and 1b would preferably be used to prepare various types of highly absorbant biocompatible dressing materials in the form of nonwovens, films, plasters, and pads.
IMCs using the substances from 2 and 3 may serve as efficient haemostatic agents for internal applications in the microfibrillar form, in the microdispersed form as dusting powders, in the form of films, granules, tablets or non-woven textile-like structures. Those preparations also display antiadhesive properties.
We have also found out that in the form of film-like cell culture matrices the latter IMCs incorporating PAGA and salts thereof as prepared according to PCT IE 98/00004 have a favourable effect on the growth of fibroblasts and keratinocytes.
While it is also possible to create IMCs using structural scleroproteins of the collagen type as disclosed in WO 9800180A, it is preferable to use the above mentioned groups of substances because of the possibility of contamination of the final product by telopeptides, viruses or pyrogens. Collagen can affect in an uncontrolled manner, the immune response of the organism because formation of antibodies can be provoked by any portion of the collagen structure even though the main determinants occur in the terminal regions of the collagen macromolecule. Removal of telopeptides only partially solves the antigenicity problem (Michaeli et al: Science, 1969, 166, 1522).
By preparing IMCs according to the invention it is possible to essentially enhance properties of the originally prepared glucoronoglucanes such as 1,4 xcex2 PAGA. For instance an intermolecular complex salt of PAGA and gelatine in one single production step can be used to prepare final products in the form of a non woven, film, microdispersed granules, or dispersions. In contrast to collagen, suitably hydrolysed gelatine is well tolerated, has no toxicity or side effects and it is a much less costly raw material. We have found out that this complex has very good haemostatic properties being about 40% higher than the original PAGA calcium sodium salt. This is despite the fact that the gelatine itself only displays a haemostatic effect after an addition of thrombin [Schwartz S. I. et al.: Principles of Surgery, St. Louis: McGraw Hill Co, 1979, p. 122-123]. In this case the absorption in the organism can be controlled by changing the composition of the complex within the range from tens of hours to several months. This complex has a higher haemostatic efficiency and can be used as an embolisation or microembolisation product. It can also be used to prepare haemostatic layers of highly absorbent multi-layer dressings or resorbable plasters, though more costly polybren or protamines could also be applied.
An important advantage of these IMCs is the fact that the compounds can be prepared within a single manufacturing operation using the hydrolytic process described in PCT IE 98/00004 which makes these products cost effective.
These IMCs can further be modified by biologically active and/or biologically acceptable substances. Because the IMCs prepared by the present procedure are either of a microdispersed or microfibrillar nature, the active substances tend to be bound uniformly and also are uniformly released in the organism without the need for other adjuvants such as microcrystalline waxes or stearates. However, the addition of such adjuvants is not excluded.
Biologically active substances which can be incorporated into the IMC may involve, for instance, antibiotics carrying at least a weak positive charge in the molecule such as cephalosporins (cephotaxin), aminoglycosides (neomycin, gentamycin, amikacin), penicillins (tikarcilin) or macrolides (erythromycin, clarithromycin) and the like.
In cases where the calcium/sodium salt of PAGA or its IMC complexes according to the invention are used as microembolisation or embolisation agents in regional chemotherapy of malign tumours, suitable types of cytostatics such as adriamycin or derivatives of 1,4-diaminoanthrachinone can be incorporated. It is also possible to use the IMCs as detaching ligands for platinum(II) based cytostatics.
Biologically acceptable substances used for modification of the IMCs include, for instance, glycerol and its polymers polyglycerols); mono, di, and certain triglycerides: polyethyleneglycols; monopropyleneglycol; block copolymers of polyethyleneoxides and polypropyleneoxides (Pluronic); starches; cyclodextines; polyvinylalcohols; cellulose and its derivatives; in general, substances that, in the concentrations used, are not irritating or toxic for the living organism while being capable of further optimising the physicomechanical properties of the final product based on the IMCs according to the invention.
The invention will be more clearly understood from the following examples of polymer complexes of glucuronoglucanes.